The customary manner of producing linear motion is to use conventional rotary motors/generators which are coupled by conventional linear convertors. These devices require many attendant cranks and linkages which are subject to wear thereby limiting the life of the apparatus. In addition, when such devices are subjected to environmental extremes, the various motor seals and other critical elements do not function properly, thereby causing equipment failure.
To partially alleviate the problems inherent in conventional rotary to linear conversion devices, linear motors/generators have been developed. However, such linear motors/generators require various seals and contacting members which tend to fail in such usage because of frictional wear of bearings and seals supporting the linear moving elements. Although lubricants have been used to reduce the frictional wear, these have been found not to function properly and tend to compromise the peformance of heat exchangers and other functional elements peculiar to refrigeration needs. To eliminate the bearing wear problem, some prior art linear motors/generators employ gas bearings having linear elements supported by gas. These gas bearings have not met with great success because they tend to lose their support at start-up and at the end of the linear stroke of the element. In the alternative, pressurized gas supplies are not generally available without adding greatly to the cost and weight of the system. Thus, in outer space where cost, weight, and simplicity are of vital importance, gas bearings are impractical.
Conventional magnetic bearings eliminate many of the attendant problems associated with other types of bearings. Conventional magnetic bearings perform exceptionally well when the element being supported is stationary or rotating about the axis. However, when linear motion is imparted, non-linear side forces are introduced which produce excessive radial movement of the element causing the element to contact the various parts of linear motors/generators. In addition, in conventional magnetic bearings the air gap between the magnetic bearing surfaces and the supported element needs to be as small as possible. The minimum air gap requirement of conventional magnetic bearings creates a number of disadvantages in linear motors/generators. One disadvantage is that with a minimum air gap any radial movement of the supported element will cause contact between the magnetic elements and the supported element causing friction and binding. Additionally, once the supported element contacts a magnetic element, the supported element will be magnetically coupled thereto. Another disadvantage is that when using a magnetic force to actuate the supported element linearly, the axial force increases proportionally with the air gap; i.e., the larger the gap the greater the force. This action directly conflicts with the minimum air gap requirement of conventional magnetic bearings. A further disadvantage associated with state of the art linear motors/generators is that they are uni-directional. The work supplied by motors/generators is only accomplished by the supported member when it linearly moves in one direction along the axis. To continue operating, the supported member must be returned to its neutral, or starting, position and the same force reapplied. This mode of operation is inefficient.
Accordingly, one object of the invention is to provide an improved linear magnetic motor/generator.
Another object of this invention is to provide a linear magnetic motor/generator which is relatively simple and economical.
Still another object of this invention is to provide a virtually friction free linear magnetic motor/generator.
A further object of the invention is to provide a linear magnetic motor/generator which operates efficiently and effectively at environmental extremes.
A still further object of this invention is to provide a linear magnetic motor/generator which maintains support throughout the operating cycle.
Another object of the invention is to provide a linear magnetic motor/generator that compensates for applied radial forces.
A further object of the invention is to provide a linear magnetic motor/generator wherein no minimum air gap requirement exists.
A still further object of the invention is to provide a bidirectionally operating linear magnetic motor/generator.